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1.
The Malay Peninsula is characterised by three north–south belts, the Western, Central, and Eastern belts based on distinct differences in stratigraphy, structure, magmatism, geophysical signatures and geological evolution. The Western Belt forms part of the Sibumasu Terrane, derived from the NW Australian Gondwana margin in the late Early Permian. The Central and Eastern Belts represent the Sukhothai Arc constructed in the Late Carboniferous–Early Permian on the margin of the Indochina Block (derived from the Gondwana margin in the Early Devonian). This arc was then separated from Indochina by back-arc spreading in the Permian. The Bentong-Raub suture zone forms the boundary between the Sibumasu Terrane (Western Belt) and Sukhothai Arc (Central and Eastern Belts) and preserves remnants of the Devonian–Permian main Palaeo-Tethys ocean basin destroyed by subduction beneath the Indochina Block/Sukhothai Arc, which produced the Permian–Triassic andesitic volcanism and I-Type granitoids observed in the Central and Eastern Belts of the Malay Peninsula. The collision between Sibumasu and the Sukhothai Arc began in Early Triassic times and was completed by the Late Triassic. Triassic cherts, turbidites and conglomerates of the Semanggol “Formation” were deposited in a fore-deep basin constructed on the leading edge of Sibumasu and the uplifted accretionary complex. Collisional crustal thickening, coupled with slab break off and rising hot asthenosphere produced the Main Range Late Triassic-earliest Jurassic S-Type granitoids that intrude the Western Belt and Bentong-Raub suture zone. The Sukhothai back-arc basin opened in the Early Permian and collapsed and closed in the Middle–Late Triassic. Marine sedimentation ceased in the Late Triassic in the Malay Peninsula due to tectonic and isostatic uplift, and Jurassic–Cretaceous continental red beds form a cover sequence. A significant Late Cretaceous tectono-thermal event affected the Peninsula with major faulting, granitoid intrusion and re-setting of palaeomagnetic signatures. 相似文献
2.
I. Metcalfe 《Journal of Asian Earth Sciences》2000,18(6)
It is proposed that the Bentong–Raub Suture Zone represents a segment of the main Devonian to Middle Triassic Palaeo-Tethys ocean, and forms the boundary between the Gondwana-derived Sibumasu and Indochina terranes. Palaeo-Tethyan oceanic ribbon-bedded cherts preserved in the suture zone range in age from Middle Devonian to Middle Permian, and mélange includes chert and limestone clasts that range in age from Lower Carboniferous to Lower Permian. This indicates that the Palaeo-Tethys opened in the Devonian, when Indochina and other Chinese blocks separated from Gondwana, and closed in the Late Triassic (Peninsular Malaysia segment). The suture zone is the result of northwards subduction of the Palaeo-Tethys ocean beneath Indochina in the Late Palaeozoic and the Triassic collision of the Sibumasu terrane with, and the underthrusting of, Indochina. Tectonostratigraphic, palaeobiogeographic and palaeomagnetic data indicate that the Sibumasu Terrane separated from Gondwana in the late Sakmarian, and then drifted rapidly northwards during the Permian–Triassic. During the Permian subduction phase, the East Malaya volcano-plutonic arc, with I-Type granitoids and intermediate to acidic volcanism, was developed on the margin of Indochina. The main structural discontinuity in Peninsular Malaysia occurs between Palaeozoic and Triassic rocks, and orogenic deformation appears to have been initiated in the Upper Permian to Lower Triassic, when Sibumasu began to collide with Indochina. During the Early to Middle Triassic, A-Type subduction and crustal thickening generated the Main Range syn- to post-orogenic granites, which were emplaced in the Late Triassic–Early Jurassic. A foredeep basin developed on the depressed margin of Sibumasu in front of the uplifted accretionary complex in which the Semanggol “Formation” rocks accumulated. The suture zone is covered by a latest Triassic, Jurassic and Cretaceous, mainly continental, red bed overlap sequence. 相似文献
3.
Present-day Asia comprises a heterogeneous collage of continental blocks, derived from the Indian–west Australian margin of eastern Gondwana, and subduction related volcanic arcs assembled by the closure of multiple Tethyan and back-arc ocean basins now represented by suture zones containing ophiolites, accretionary complexes and remnants of ocean island arcs. The Phanerozoic evolution of the region is the result of more than 400 million years of continental dispersion from Gondwana and plate tectonic convergence, collision and accretion. This involved successive dispersion of continental blocks, the northwards translation of these, and their amalgamation and accretion to form present-day Asia. Separation and northwards migration of the various continental terranes/blocks from Gondwana occurred in three phases linked with the successive opening and closure of three intervening Tethyan oceans, the Palaeo-Tethys (Devonian–Triassic), Meso-Tethys (late Early Permian–Late Cretaceous) and Ceno-Tethys (Late Triassic–Late Cretaceous). The first group of continental blocks dispersed from Gondwana in the Devonian, opening the Palaeo-Tethys behind them, and included the North China, Tarim, South China and Indochina blocks (including West Sumatra and West Burma). Remnants of the main Palaeo-Tethys ocean are now preserved within the Longmu Co-Shuanghu, Changning–Menglian, Chiang Mai/Inthanon and Bentong–Raub Suture Zones. During northwards subduction of the Palaeo-Tethys, the Sukhothai Arc was constructed on the margin of South China–Indochina and separated from those terranes by a short-lived back-arc basin now represented by the Jinghong, Nan–Uttaradit and Sra Kaeo Sutures. Concurrently, a second continental sliver or collage of blocks (Cimmerian continent) rifted and separated from northern Gondwana and the Meso-Tethys opened in the late Early Permian between these separating blocks and Gondwana. The eastern Cimmerian continent, including the South Qiangtang block and Sibumasu Terrane (including the Baoshan and Tengchong blocks of Yunnan) collided with the Sukhothai Arc and South China/Indochina in the Triassic, closing the Palaeo-Tethys. A third collage of continental blocks, including the Lhasa block, South West Borneo and East Java–West Sulawesi (now identified as the missing “Banda” and “Argoland” blocks) separated from NW Australia in the Late Triassic–Late Jurassic by opening of the Ceno-Tethys and accreted to SE Sundaland by subduction of the Meso-Tethys in the Cretaceous. 相似文献
4.
The Indosinian Orogeny in Thailand is often viewed as having developed between strongly linear terranes, which today trend approximately N–S. The terranes were subsequently disrupted by later tectonics, particularly NW–SE trending Cenozoic strike-slip faults. The ENE–WSW to NE–SW striking thrusts and folds in the Khao Khwang Platform area of the Saraburi Group on the SW margin of the Indochina Terrane are not easily explained in the context of this traditional view. Reversal of the clockwise rotation shown to have affected the block north of the Mae Ping Fault zone only enhances the E–W orientation of structures in the fold and thrust belt, and moves the belt further east towards Cambodia. One solution for the trend that fits better with regional understanding from hydrocarbon exploration of the Khorat Plateau is that the Indochina Terrane was actually a series of continental blocks, separated by Permian rifting. During the Early Triassic the early stages of collision (South China-Cathaysian Terrane collision with Vietnam Indochina) resulted in the amalgamation of disparate blocks that now form the Indochina Terrane by closure along the rifts. At the same time or following on from the collision there was closure of the back-arc area between Indochina and the Sukhothai zone. The rift basins, were thrusted and inverted during the early stages of the Indosinian orogeny, and only underwent minor reactivated when later Sibumasu collided with Sukhothai Zone-Indochina Terrane margin during the Late Triassic. The scenario described above requires the presence of a (minor) E–W trending suture in NW Cambodia. Evidence for this suture is suggested by the presence of Permo-Triassic calc-alkaline volcanism. 相似文献
5.
Tectonic framework and Phanerozoic evolution of Sundaland 总被引：1，自引：0，他引：1
Ian Metcalfe 《Gondwana Research》2011,19(1):3-21
Sundaland comprises a heterogeneous collage of continental blocks derived from the India–Australian margin of eastern Gondwana and assembled by the closure of multiple Tethyan and back-arc ocean basins now represented by suture zones. The continental core of Sundaland comprises a western Sibumasu block and an eastern Indochina–East Malaya block with an island arc terrane, the Sukhothai Island Arc System, comprising the Linchang, Sukhothai and Chanthaburi blocks sandwiched between. This island arc formed on the margin of Indochina–East Malaya, and then separated by back-arc spreading in the Permian. The Jinghong, Nan–Uttaradit and Sra Kaeo Sutures represent this closed back-arc basin. The Palaeo-Tethys is represented to the west by the Changning–Menglian, Chiang Mai/Inthanon and Bentong–Raub Suture Zones. The West Sumatra block, and possibly the West Burma block, rifted and separated from Gondwana, along with Indochina and East Malaya in the Devonian and were accreted to the Sundaland core in the Triassic. West Burma is now considered to be probably Cathaysian in nature and similar to West Sumatra, from which it was separated by opening of the Andaman Sea basin. South West Borneo and/or East Java-West Sulawesi are now tentatively identified as the missing “Argoland” which must have separated from NW Australia in the Jurassic and these were accreted to SE Sundaland in the Cretaceous. Revised palaeogeographic reconstructions illustrating the tectonic and palaeogeographic evolution of Sundaland and adjacent regions are presented. 相似文献
6.
U–Pb dating of detrital zircons was performed on mélange-hosted lithic and basaltic sandstones from the Inthanon Zone in northern Thailand to determine the timing of accretion and arc activity associated with Paleo-Tethys subduction. The detrital zircons have peak ages at 3400–3200, 2600–2400, 1000–700, 600–400, and 300–250 Ma, similar to the peaks ages of detrital zircons associated with other circum-Paleo-Tethys subduction zones. We identified two types of sandstone in the study area based on the youngest detrital zircon ages: Type 1 sandstones have Late Carboniferous youngest zircon U–Pb ages of 308 ± 14 and 300 ± 16 Ma, older than associated radiolarian chert blocks within the same outcrop. In contrast, Type 2 sandstones have youngest zircon U–Pb ages of 238 ± 10 and 236 ± 15 Ma, suggesting a Middle Triassic maximum depositional age. The youngest detrital zircons in Type 1 sandstones were derived from a Late Carboniferous–Early Permian ‘missing’ arc, suggesting that the Sukhothai Arc was active during sedimentation. The data presented within this study provide information on the development of the Sukhothai Arc, and further suggest that subduction of the Paleo-Tethyan oceanic plate beneath the Indochina Block had already commenced by the Late Carboniferous. Significant Middle Triassic arc magmatism, following the Late Carboniferous–Early Permian arc activity, is inferred from the presence of conspicuous detrital zircon U–Pb age peaks in Type 2 sandstones and the igneous rock record of the Sukhothai Arc. In contrast, only minimal arc activity occurred during the Middle Permian–earliest Triassic. Type 1 sandstones were deposited between the Late Permian and the earliest Triassic, after the deposition of associated Middle–Late Permian cherts that occur in the same mélanges and during a hiatus in Sukhothai Arc magmatism. In contrast, Type 2 sandstones were deposited during the Middle Triassic, coincident with the timing of maximum magmatism in the Sukhothai Arc, as evidenced by the presence of abundant Middle Triassic detrital zircons. These two types of sandstone were probably derived from discrete accretionary units in an original accretionary prism that was located along the western margin of the Sukhothai Arc. 相似文献
7.
Tectonic implications of the Nan Suture Zone and its relationship to the Sukhothai Fold Belt, Northern Thailand 总被引：2，自引：0，他引：2
The Nan Suture and the Sukhothai Fold Belt reflect the processes associated with the collision between the Shan-Thai and Indochina Terranes in southeast Asia. The Shan-Thai Terrane rifted from Gondwana in the Early Permian. As it drifted north a subduction complex developed along its northern margin. The Nan serpentinitic melange is a thrust slice within the Pha Som Metamorphic Complex and in total this unit is a Late Permian accretionary complex containing offscraped blocks from subducted oceanic crust of Carboniferous and Permian age. The deformational style within the Pha Som Metamorphic Complex supports a west-dipping subduction zone. The Late Permian to Late Triassic fore-arc basin sediments are preserved in the Sukhothai Fold Belt and include a near continuous sedimentary record, at least locally. The whole sequence was folded and complexly thrust in the Late Triassic as a result of the collision. Late syn- to post-kinematic granites place an upper limit of 200 Ma on the time of collision. Post-orogenic sediments prograded across the suture in the Jurassic. 相似文献
8.
Volcanoplutonic complexes in NE Vietnam have recently been interpreted as intraplate products of the Emeishan plume. Alternatively, mafic–ultramafic rocks have been considered as dismembered Palaeotethyan ophiolites juxtaposed along a tectonic mélange zone. New U–Pb zircon geochronological and geochemical datasets presented here suggest a complex geological history that records collision between the Indochina–South China blocks. Mafic–ultramafic rocks exposed within a tectonic mélange (Song Hien Tectonic Zone) include sub-alkaline pillow basalts that define two geochemically distinct ophiolitic suites (SH-1: N-MORB-like, SH-2: transitional E-MORB-like). Both suites have geochemical signatures suggestive of crustal contamination, compatible with a volcanic passive margin/rift setting. We suggest that SH-1 basalts may correlate with the Devonian–Carboniferous Jinshajiang–Ailaoshan–Song Ma branch of the Palaeotethys and form part of the associated Dian–Qiong belt, whereas SH-2 basalts are co-magmatic with Middle–Late Permian mafic–ultramafic intrusive rocks (dolerites, gabbros, peridotites) that developed in a rift basin, most likely on the margin of the down-going South China plate during west-vergent subduction beneath Indochina. During continental orogenesis and thrust stacking, these ophiolitic rocks were juxtaposed with other lithotectonic blocks within the Song Hien Tectonic Zone. Post-collisional relaxation led to the development of a rift basin (Song Hien rift) comprising Late Permian–Triassic volcano-sedimentary strata including < 270–265 Ma terrigenous sandstones, < 252 Ma mudstones, and c. 254–248 Ma felsic effusives. Granites and granodiorites were emplaced across NE Vietnam between c. 252 and 245 Ma in a syn- to post-collisional setting. The Late Permian–Early Triassic felsic magmatic rocks best correlate with coeval rocks in SW Guangxi and the Central and Western Ailaoshan fold belts (China) and the Truong Son fold belt (Vietnam); together they signal the final to post-collisional stages of Indochina–South China collision. We demonstrate that the analysed magmatic rocks in the Lo-Gam–Song Hien domains of NE Vietnam are not genetically linked to the Emeishan Large Igneous Province in the Yangtze block of South China, as has been previously widely proposed. 相似文献
9.
《International Geology Review》2012,54(8):976-993
The time of final closure of the Palaeo-Tethys and the Sibumasu-Indochina collision in Southeast Asia represents a major unresolved geologic problem. Here, we present zircon chronology, whole-rock elemental, Sr–Nd, and zircon Hf isotopic geochemistry for newly discovered mafic dikes from the northern segment of the Sibumasu terrane, to provide constraints on this issue. Zircon U–Pb data indicate that the dikes were emplaced at 240 ± 3 Ma. These are the earliest Mesozoic magmatic rocks reported so far in the Sibumasu terrane, the late Palaeozoic passive margin of the Palaeo-Tethys. They are subalkaline tholeiites, showing geochemical characteristics similar to those of enriched mid-ocean ridge basalts (E-MORBs). They have 87Sr/86Sr(t) ratios of 0.703161–0.703826, ?Nd(t) of +4.8 to +7.5, and zircon ?Hf(t) of +9.2 to +13.3, implying strong mantle depletion. They were derived by partial melting of asthenospheric mantle and underwent subsequent fractional crystallization and lithospheric assimilation. The geologic–petrologic evidence suggests that the mafic dikes were generated in a collisional setting, when suturing of the Baoshan and Simao subterranes (the two subterranes are part of the Sibumasu and Indochina terranes, respectively) occurred. These early Middle Triassic mafic dikes provide an upper limit for Sibumasu–Indochina collision. In conjunction with previous work, we conclude that the final closure of the Palaeo-Tethys and collision of the Sibumasu and Indochina terranes took place during the late Permian to Early Triassic. 相似文献
10.
Nan-Uttaradit suture zone in northern Thailand is a narrow N-S trending and discontinuous ophiolite belt along the Nan River (Barr and MacDonald, 1987). It was interpreted as the Paleo-Tethys oceanic remnants that separate Shan-Thai (Sibumasu) terrane and Indo-china terrane (Bunopas, 1981; Hada, 1999), and rein-terpreted as the boundary of Sukhothai (or Simao) terrane and the Indochina terrane that representing a segment of the back-arc basin (Barr and MacDonald, 1991; Ueno and Hisada, 2001; Metcalfe, 2006; Ferrari et al., 2008; Sone and Metcalfe, 2008). This zone is dominated by Carboniferous to Permian Pha Som Metamorphic Complex (Hess and Koch, 1975). The Pha Som Metamorphic Complex consists of several tectonostratigraphic slices of volcanic rocks, schists, meta-greywacke, serpentinite and bedded chert. And it is in fault contact with Pak Pat volcanic rocks. Both of Pha Som Metamorphic Complex and Pak Pat volcanic rocks are covered by the Upper Triassic and the Juras-sic red sandstones with angular unconformity. Previ-ous studies mainly focused on the amalgamation epi-sodes of the Sukhothai terrane and Indochina terrane. The Late Carboniferous to Early Permian age of the opening of the basin was proposed by some authors (Singharajwarapan and Berry, 2000; Metcalfe, 2006; Ferrari et al., 2008) on the basis of the regional strati-graphy, different dating of cherts, and schists from the Pha Som Metamorphic Complex. 相似文献
11.
《China Geology》2021,4(4):630-643
The Nan Suture and Sukhothai Arc Terrane are products of the eastward subduction of the Paleotethyan Ocean during the Late Carboniferous to Triassic. However, their footprints in northwestern Laos are poorly constrained. New geochronological and geochemical data presented in this study demonstrate a Late Permian origin for the andesitic rocks in the B.Xiengnou area rather than Late Triassic. The breccia-bearing andesitic tuff in the B.On ultramafic complex yield a zircon U-Pb age of 260 ± 1.4 Ma, geochemically displaying a MORB-like signature. The andesitic tuff in the B.Kiophoulan-B.Houayhak belt gave the U-Pb age of 254 ± 1.3 Ma, with arc-like geochemical affinity. By combining geochronological and geochemical data from the Nan Suture and Sukhothai Arc Terrane, the authors suggest that the andesitic rocks in the B.On ultramafic complex formed in a back-arc basin background, which connected the Jinghong and Nan back-arc basin during the Permian; while the andesitic tuff in the B.Kiophoulan-B.Houayhak belt erupted in the Sukhothai continental arc setting.©2021 China Geology Editorial Office. 相似文献
12.
The study area, Nan Province, northern Thailand is geotectonically situated within the Nan-Uttaradit Suture, the once back-arc basin between the Sukhothai Zone and Indochina Block. Permian Fusulinacean fauna from limestone blocks within the suture has been investigated and the Nan area has been mapped in detail. These may provide the useful information for understanding the faunal assemblage and overall ge-ometry of stratigraphic successions in the basin. The strata were intensely folded and thrust. Scattered Per-mian limestones found in Nan area are blocks within shale interbedded with tuffaceous rock. The contact between this unit and the adjacent units, the strongly foliated shale and tuffaceous sedimentary strata that are mildly metamorphosed and giving phyllitic tex-tures, has been interpreted as a west-dipping normal fault, namely the Pha Sing Fault. This fault runs par-allel to the Highway no.1080 (Nan-Tha Wang Pha). Middle and early Late Permian fusulinacean fauna found in the Nan area contains Neoschwagerina, Pseudodoliolina, Colania, Lepidolina, and Colaniella. Additionally, late Early Permian fusulinacean and Middle Triassic radiolarian fauna have been reported in this area (e.g., Fontaine, 2002; Saesaengseerung et al. 2008). These paleontological data show the existence of Nan Back-arc Basin during late Early Permian (Artin-skian) to Middle Triassic. Moreover, the similarity of fusulinacean assemblage yielding Permian limestone blocks of the Nan Back-arc Basin and the ones of the Indochina Block has been interpreted that the Permian limestone blocks in the Nan Back-arc Basin were part of the continental shelf within the Indochina Block. 相似文献
13.
西南三江地区洋板块地层特征及构造演化 总被引：3，自引：3，他引：0
以大地构造研究为主导,初步梳理了三江地区洋板块地层系统的分布及其构造演化规律。本文阐述了三江地区经历原-古特提斯大洋连续演化、分阶段拼贴增生至最终俯冲消亡的地质演化历程。甘孜-理塘弧后洋盆于早石炭世打开,二叠纪—中三叠世进入顶峰扩张期,晚三叠世洋盆萎缩引起向西俯冲,最终在晚三叠世末局部地区保留残留海。哀牢山弧后洋盆不晚于早石炭世形成,早石炭世—早二叠世整体扩张发育,早二叠世末或晚二叠世初开始向西俯冲,晚三叠世最终完全关闭。金沙江洋盆早石炭世时已扩张成洋,到早二叠世晚期开始俯冲,石炭纪—早二叠世早期是金沙江洋盆扩张的主体时期,早二叠世晚期至早、中三叠世俯冲消亡。澜沧江弧后洋盆中晚泥盆世开始扩张,在石炭纪—早二叠世发育为成熟洋盆,早二叠世晚期洋内俯冲形成洋内弧,晚二叠世—早、中三叠世双向俯冲消亡。昌宁-孟连洋为特提斯洋主带,具有原-古特提斯洋连续演化的地质记录,晚奥陶世开始向东俯冲消减,二叠纪末、早三叠世发生弧-陆碰撞作用,昌宁-孟连洋盆闭合。 相似文献
14.
《Gondwana Research》2013,24(4):1429-1454
Different hypotheses have been proposed for the origin and pre-Cenozoic evolution of the Tibetan Plateau as a result of several collision events between a series of Gondwana-derived terranes (e.g., Qiangtang, Lhasa and India) and Asian continent since the early Paleozoic. This paper reviews and reevaluates these hypotheses in light of new data from Tibet including (1) the distribution of major tectonic boundaries and suture zones, (2) basement rocks and their sedimentary covers, (3) magmatic suites, and (4) detrital zircon constraints from Paleozoic metasedimentary rocks. The Western Qiangtang, Amdo, and Tethyan Himalaya terranes have the Indian Gondwana origin, whereas the Lhasa Terrane shows an Australian Gondwana affinity. The Cambrian magmatic record in the Lhasa Terrane resulted from the subduction of the proto-Tethyan Ocean lithosphere beneath the Australian Gondwana. The newly identified late Devonian granitoids in the southern margin of the Lhasa Terrane may represent an extensional magmatic event associated with its rifting, which ultimately resulted in the opening of the Songdo Tethyan Ocean. The Lhasa−northern Australia collision at ~ 263 Ma was likely responsible for the initiation of a southward-dipping subduction of the Bangong-Nujiang Tethyan Oceanic lithosphere. The Yarlung-Zangbo Tethyan Ocean opened as a back-arc basin in the late Triassic, leading to the separation of the Lhasa Terrane from northern Australia. The subsequent northward subduction of the Yarlung-Zangbo Tethyan Ocean lithosphere beneath the Lhasa Terrane may have been triggered by the Qiangtang–Lhasa collision in the earliest Cretaceous. The mafic dike swarms (ca. 284 Ma) in the Western Qiangtang originated from the Panjal plume activity that resulted in continental rifting and its separation from the northern Indian continent. The subsequent collision of the Western Qiangtang with the Eastern Qiangtang in the middle Triassic was followed by slab breakoff that led to the exhumation of the Qiangtang metamorphic rocks. This collision may have caused the northward subduction initiation of the Bangong-Nujiang Ocean lithosphere beneath the Western Qiangtang. Collision-related coeval igneous rocks occurring on both sides of the suture zone and the within-plate basalt affinity of associated mafic lithologies suggest slab breakoff-induced magmatism in a continent−continent collision zone. This zone may be the site of net continental crust growth, as exemplified by the Tibetan Plateau. 相似文献
15.
16.
Inga Sevastjanova Benjamin Clements Robert Hall Elena A. Belousova William L. Griffin Norman Pearson 《Gondwana Research》2011,19(4):1024-1039
The Malay Peninsula lies on two continental blocks, Sibumasu and East Malaya, which are intruded by granitoids in two provinces: the Main Range and Eastern. Previous models propose that Permian–Triassic granitoids are subduction-related and syn-to post-collisional. We present 752 U–Pb analyses that were carried out on zircons from river sands in the Malay Peninsula; of these, 243 grains were selected for Hf-isotope analyses. Our data suggest a more complex Sibumasu–East Malaya collision history. 176Hf/177Hfi ratios reveal that Permian–Triassic zircons were sourced from three magmatic suites: (a) Permian crustally-derived granitoids, (b) Early-Middle Triassic granitoids with mixed mantle–crust sources, and (c) Late Triassic crustally-derived granitoids. This suggests three Permian–Triassic episodes of magmatism in the Malay Peninsula, two of which occurred in the Eastern Province. Although the exact timing of the Sibumasu–East Malaya collision remains unresolved, current data suggest that it occurred before the Late Triassic, probably in Late Permian–Early Triassic. Our data also indicate that Sibumasu and East Malaya basements are chronologically heterogeneous, but predominantly of Proterozoic age. Some basement may be Neoarchaean but there is no evidence for basement older than 2.8 Ga. Finally, we show that Hf-isotope signatures of Triassic zircons can be used as provenance indicators. 相似文献
17.
An alternative model for the geodynamic evolution of Southeast Asia is proposed and inserted in a modern plate tectonic model. The reconstruction methodology is based on dynamic plate boundaries, constrained by data such as spreading rates and subduction velocities; in this way it differs from classical continental drift models proposed so far. The different interpretations about the location of the Palaeotethys suture in Thailand are revised, the Tertiary Mae Yuam fault is seen as the emplacement of the suture. East of the suture we identify an Indochina derived terrane for which we keep the name Shan–Thai, formerly used to identify the Cimmerian block present in Southeast Asia, now called Sibumasu. This nomenclatural choice was made on the basis of the geographic location of the terrane (Eastern Shan States in Burma and Central Thailand) and in order not to introduce new confusing terminology. The closure of the Eastern Palaeotethys is related to a southward subduction of the ocean, that triggered the Eastern Neotethys to open as a back-arc, due to the presence of Late Carboniferous–Early Permian arc magmatism in Mergui (Burma) and in the Lhasa block (South Tibet), and to the absence of arc magmatism of the same age East of the suture. In order to explain the presence of Carboniferous–Early Permian and Permo-Triassic volcanic arcs in Cambodia, Upper Triassic magmatism in Eastern Vietnam and Lower Permian–Middle Permian arc volcanites in Western Sumatra, we introduce the Orang Laut terranes concept. These terranes were detached from Indochina and South China during back-arc opening of the Poko–Song Ma system, due to the westward subduction of the Palaeopacific. This also explains the location of the Cathaysian West Sumatra block to the West of the Cimmerian Sibumasu block. 相似文献
18.
The Late Permian–early Middle Triassic strata of the northern West Qinling area, northeastern Tibetan Plateau, are composed of sediment gravity flow deposits. Detailed sedimentary facies analysis indicates these strata were deposited in three successive deep-marine environments. The Late Permian–early Early Triassic strata of the Maomaolong Formation and the lowest part of the Longwuhe Formation define a NW–SE trending proximal slope environment. Facies of the Early Triassic strata composing the middle and upper Longwuhe Formation are consistent with deposition in a base-of-slope apron environment, whereas facies of the Middle Triassic Anisian age Gulangdi Formation are more closely associated with a base-of-slope fan depositional environment. The lithofacies and the spatial–temporal changes in paleocurrent data from these strata suggest the opening of a continental margin back-arc basin system during Late Permian to early Middle Triassic time in the northern West Qinling. U–Pb zircon ages for geochemically varied igneous rocks with diabasic through granitic compositions intruded into these deep-marine strata range from 250 to 234 Ma. These observations are consistent with extensional back-arc basin development and rifting between the Permian–Triassic Eastern Kunlun arc and North China block during the continent–continent collision and underthrusting of the South China block northward beneath the Qinling terrane of the North China block. Deep-marine sedimentation ended in the northern West Qinling by the Middle Triassic Ladinian age, but started in the southern West Qinling and Songpan-Ganzi to the south. We attribute these observations to southward directed rollback of Paleo-Tethys oceanic lithosphere, continued attenuation of the West Qinling on the upper plate, local post-rift isostatic compensation in the northern West Qinling area, and continued opening of a back-arc basin in the southern West Qinling and Songpan-Ganzi. Rollback and back-arc basin development during Late Permian to early Middle Triassic time in the West Qinling area explains: the truncated map pattern of the Eastern Kunlun arc, the age difference of deep-marine sediment gravity flow deposits between the Late Permian–early Middle Triassic northern West Qinling and the late Middle Triassic–Late Triassic southern West Qinling and Songpan-Ganzi, and the discontinuous trace of ophiolitic rocks associated with the Anyemaqen-Kunlun suture. 相似文献
19.
Zircon U–Pb, mica 40Ar/39Ar ages and geochemistry of the Permo-Triassic mafic to intermediate dyke swarms at the south-western margin of the Indochina Terrane, central Thailand, are reported here and used to decipher the timing of the Sukhothai-Indochina & Sibumasu-Indochina collisions during the Permo-Triassic stages of the Indosinian Orogeny. The mafic dyke swarms in the folded layers of the Khao Khwang Fold–Thrust Belt (KKFTB) were emplaced between the Late Permian and the Late Triassic. The volcanic rocks range from slightly tholeiitic to mostly calc-alkalic, but can be subdivided into three different volcanic groups on the basis of trace and incompatible element abundances such as Ni, Cr, P, Co, and Th. However, all the groups present similar chemical footprints and are enriched in large ion lithophile elements (LILEs) (Rb, Ba, Sr, Pb) and light rare earth elements (LREEs), and depleted in HFSE such as Nb, and Ti highlighting the volcanic arc nature of the system. Isotopically, the three groups are characterized by subtle differences in εNd(t) values (from + 3.2 to + 5.2) and initial 87Sr/86Sr ratios (from 0.7056 to 0.7067). The KKFTB mafic dykes share a few geochemical characteristics of the mafic dykes from the Chiang Khong volcanic suite in the Sukhothai terrane, and from the Loei volcanic belt in northern Indochina. These geochemical features suggest that the KKFTB mafic dykes, and the volcanic rocks in central-northern Thailand, were likely emplaced in a similar orogenic setting. The rocks of Group III are interpreted to have intruded from the Early Triassic (255 ± 6 Ma) to the Late Triassic (207 ± 2 Ma), and were probably sourced from a more crustally contaminated magma. 相似文献
20.
The Truong Son Fold Belt (TSFB) is characterised by Late Carboniferous-Late Triassic metamorphic, volcanic and plutonic rocks, the product of accretion of the Indochina Terrane onto the South China Terrane and a range of composite subduction, collision and extensional events. This study discusses geochronological and geochemical data obtained from a dioritic intrusion and rhyolitic tuff mapped in the Donken area of SE Laos, and previously assigned to the Permian Antoum Granodiorite rock suite within the TSFB. Magmatic zircon U-Pb Q-ICP-MS dating undertaken in this study suggests ages of ca 470 ± 2 Ma for the diorite and ca 476 ± 1.5 Ma for a proximal rhyolitic tuff.Whole-rock geochemistry of both units suggests a subduction-related island arc environment, with calc-alkaline and tholeiitic affinities for the diorite and tuff respectively. The intrusion also exhibits an adakitic signature (high Sr, low Y and HREE contents) suggesting that Ordovician magmatism also occurred within the Indochina Terrane, associated with an enigmatic, early Gondwana subduction event. This intrusion appears part of a broader, bilateral Early Ordovician magmatism, newly linked to the south-east subduction of the Tamky-Phuoc Son Ocean underneath the Kontum terrane, and a north-west subduction beneath the Truong Son terrane. Significantly, sub-economic hydrothermal Cu mineralisation observed within the dioritic intrusion, hints at the presence of local Ordovician, porphyry-style base metal enrichment. 相似文献